Many different types of data storage systems exist and are being used to store data cartridges at known locations and to retrieve desired data cartridges so that data may be written to or read from the data cartridges. Such data storage systems are often referred to as "juke box" data storage systems, particularly if they can accommodate a large number of individual data cartridges.
A typical juke box data storage system may include one or more different types of cartridge receiving devices for holding the various data cartridges. For example, one type of cartridge receiving device may comprise a cartridge storage rack or "magazine" while another type of cartridge receiving device may comprise a cartridge read/write device. The cartridge storage racks or magazines serve to provide storage locations for the data cartridges and are often arranged so that they form one or more vertical stacks, although other configurations are possible. The cartridge read/write device may be located at any convenient location within the data storage system.
The data storage system may also be provided with a moveable cartridge picker assembly or simply "picker" for transporting the data cartridges between the various cartridge receiving devices, e.g., between the cartridge storage racks and the cartridge read/write devices. A typical picker may also be provided with a cartridge plunge mechanism or "thumb" assembly for engaging the various data cartridges contained in the cartridge receiving devices and for drawing them into the picker. A picker positioning system associated with the cartridge picker assembly may be used to move the cartridge picker assembly along the various cartridge receiving devices.
Data storage systems of the type described above are usually connected to a host computer system which may be used to access or store data on the data cartridges. For example, if the host computer system issues a request for data contained on a particular data cartridge, a control system associated with the data storage system will actuate the picker positioning system to move the picker assembly along the cartridge storage racks until the picker assembly is positioned adjacent the desired data cartridge. The cartridge plunge mechanism or "thumb" assembly associated with the picker assembly may then remove the data cartridge from the cartridge storage rack and draw it into the picker assembly. The picker positioning system may then be actuated to move the picker assembly to the appropriate cartridge read/write device. Once properly positioned adjacent the cartridge read/write device, the thumb assembly may insert the selected data cartridge into the cartridge read/write device so that the host computer may thereafter read data from or write data to the data cartridge. After the read/write operation is complete, the thumb assembly may be actuated to remove the data cartridge from the cartridge read/write device. The picker assembly may thereafter return the data cartridge to the appropriate location in the cartridge storage rack.
A typical cartridge plunge mechanism or "thumb" assembly is usually slidably mounted to the picker and is provided with a thumb actuator system to move the thumb assembly toward and away from a cartridge access end of the picker. For example, if it is desired to retrieve a data cartridge from a cartridge receiving device, the thumb actuator system moves the thumb assembly toward the cartridge access end of the picker so that the thumb assembly can engage or "grab" the data cartridge. Thereafter, the thumb actuator system may retract the thumb assembly and engaged data cartridge into the picker. If it is desired to load the data cartridge into the cartridge receiving device, then the thumb actuator moves the thumb assembly and data cartridge toward the cartridge access end of the picker, and inserts the data cartridge into the cartridge receiving device.
The thumb assembly may utilize any of a wide variety of devices to allow the thumb assembly to transfer the cartridge between the cartridge picker assembly and a cartridge receiving device. For example, one type of cartridge engaging device comprises a plurality of jaw members which grip the sides of a cartridge. In this system, the jaws maintain their hold on a cartridge using friction. In order to reliably grip a cartridge, the jaws must be made of a material having a high coefficient of friction with the data cartridge. This requirement may necessitate the use of relatively expensive materials for the jaws or the use of multiple materials such as a rigid plastic core and a rubber coating. The jaws also tend to be bulky due to the strength requirements in a friction system. This results in relatively large gaps between cartridges to allow the jaws to reach in between adjacent cartridges. Furthermore, the jaws must clamp firmly around the data cartridge, requiring a bulky actuator system.
Another type of cartridge engaging device may comprise a latch member of "finger" having a hooked end to engage in a notch in the side of a data cartridge. Currently known finger systems require the use of a track on the inside of the picker frame to cause the finger to splay down below the side of a data cartridge as the thumb and finger assemblies are moved toward the cartridge.
Once the finger has moved past the face of the cartridge and cleared the edge, the track allows the finger to move up toward the side of the cartridge under the tension of a spring. When the hooked end of the finger moves over the notch in the side of the cartridge, the spring pulls the hooked end of the finger up into the notch, allowing the thumb assembly to thereafter retract and pull the cartridge into the picker. In order to insert the cartridge into a cartridge receiving device, the thumb assembly pushes the cartridge, with the finger still engaged, into the device. A gate on the inside of the picker frame then causes the finger to splay away from the cartridge, disengaging the hooked end of the finger from the notch in the side of the cartridge, before the thumb assembly and finger can retract and leave the cartridge in the device.
Finger assemblies of the type described above have several advantages over friction jaws, such as needing only one finger rather than multiple jaws. The finger may also be made of inexpensive plastic, as the strength and coefficient of friction requirements are much lower. A finger assembly is also less prone to inadvertently disengage from the cartridge, as the positive engagement of the hooked end in the notch is more secure than a friction grip on the sides of a cartridge.
However, the track and gate system that is required to move the finger away from the cartridge adds complexity to the picker frame. The additional parts required add to the size and cost of the picker and lower reliability. Furthermore, if the gate malfunctions and the finger disengages from the cartridge, error recovery can be difficult if the cartridge is dropped before it is correctly placed in a cartridge receiving device.
Consequently, a need exists for an improved finger assembly to engage a data cartridge. In particular, a need exists for a finger assembly which can more easily be splayed away from the data cartridge using fewer and less expensive components.